Image forming apparatus

Abstract

An image forming apparatus, including: a photosensitive member; a light source configured to emit a light beam; a deflecting unit configured to deflect the light beam to scan the photosensitive member to form an electrostatic latent image and having a rotary polygon mirror and a motor configured to rotate the rotary polygon mirror; a housing provided with the photosensitive member, the light source, and the deflecting unit; a temperature detecting unit configured to detect a temperature; and a control unit configured to pre-rotate the rotary polygon mirror before a start signal for image formation and to rotate, after the start signal, the rotary polygon mirror at a rotation speed higher than a rotation speed for pre-rotation of the rotary polygon mirror, wherein the control unit sets a target value of the rotation speed for the pre-rotation based on a result of detection by the temperature detecting unit.

What is claimed is: 
     
       1. An image forming apparatus, comprising:
 a photosensitive member; 
 a light source configured to emit a light beam based on image data to form an electrostatic latent image on the photosensitive member; 
 a deflecting unit configured to deflect the light beam so that the light beam scans the photosensitive member, the deflecting unit comprising a rotary polygon mirror and a motor configured to rotate the rotary polygon mirror; 
 a housing provided with the photosensitive member, the light source, and the deflecting unit; 
 a temperature detecting unit configured to detect a temperature of the motor; and 
 a control unit configured to pre-rotate the rotary polygon mirror before a start signal for instructing a start of image formation is generated, and configured to rotate, after the start signal is generated, the rotary polygon mirror at a rotation speed which is higher than a rotation speed for pre-rotation of the rotary polygon mirror, 
 wherein the control unit sets a target value of the rotation speed for the pre-rotation of the rotary polygon mirror based on a result of detection by the temperature detecting unit, and 
 wherein, when the temperature detected by the temperature detecting unit is a first temperature, the control unit sets the target value to a first rotation speed, and, when the temperature detected by the temperature detecting unit is a second temperature which is higher than the first temperature, the control unit sets the target value to a second rotation speed which is lower than the first rotation speed. 
 
     
     
       2. An image forming apparatus according to  claim 1 , further comprising a setting unit in which the target value for the pre-rotation of the rotary polygon mirror is set,
 wherein the control unit sets the target value in the setting unit based on the result of the detection by the temperature detecting unit. 
 
     
     
       3. An image forming apparatus according to  claim 1 , further comprising a light scanning apparatus, the light scanning apparatus comprising:
 the light source; 
 the rotary polygon mirror; 
 the temperature detecting unit; and 
 an optical box containing the rotary polygon mirror and the temperature detecting unit, 
 wherein the control unit sets the target value based on the result of the detection by the temperature detecting unit contained in the optical box. 
 
     
     
       4. An image forming apparatus according to  claim 1 , further comprising a reading apparatus, the reading apparatus comprising:
 a reading unit configured to read an original; 
 a first original placing portion on which the original is placed so that the reading unit reads the original; 
 an original pressure cover configured to be opened and closed with respect to the first original placing portion; and 
 a second original placing portion on which the original to be conveyed to a reading position in which the reading unit reads the original is placed, 
 wherein, when the original pressure cover is operated in a state in which the rotary polygon mirror is stopped or when the original is placed on the second original placing portion in a state in which the rotary polygon mirror is stopped, the control unit starts to rotate the rotary polygon mirror. 
 
     
     
       5. An image forming apparatus according to  claim 1 , further comprising an operating portion, the operating portion comprising:
 a setting button configured to set image formation conditions; and 
 an instruction button configured to instruct the start of the image formation, 
 wherein, when at least one of the setting button and the instruction button is pressed down in a state in which the rotary polygon mirror is stopped, the control unit starts to rotate the rotary polygon mirror. 
 
     
     
       6. An image forming apparatus according to  claim 1 , further comprising a display portion configured to set image formation conditions,
 wherein, when a process on the display portion is performed in a state in which the rotary polygon mirror is stopped, the control unit starts to rotate the rotary polygon mirror. 
 
     
     
       7. An image forming apparatus according to  claim 1 , wherein the temperature detecting unit detects a temperature of the motor or an ambient temperature of the motor. 
     
     
       8. An image forming apparatus according to  claim 1 , further comprising a lapsed time obtaining unit configured to obtain a lapsed time from when a previous image formation is completed until a current rotation of the motor is started,
 wherein, when the lapsed time obtained by the lapsed time obtaining unit is a first time period, the control unit sets the target value to a first rotation speed, and, when the lapsed time obtained by the lapsed time obtaining unit is a second time period which is shorter than the first time period, the control unit sets the target value to a second rotation speed which is lower than the first rotation speed. 
 
     
     
       9. An image forming apparatus according to  claim 1 , further comprising a total operation time obtaining unit configured to obtain a total operation time of the motor,
 wherein, when the total operation time obtained by the total operation time obtaining unit is a first time period, the control unit sets the target value to a first rotation speed, and, when the total operation time obtained by the total operation time obtaining unit is a second time period which is shorter than the first time period, the control unit sets the target value to a second rotation speed which is lower than the first rotation speed. 
 
     
     
       10. An image forming apparatus according to  claim 1 , the temperature detecting unit is provided in the housing. 
     
     
       11. An image forming apparatus, comprising:
 a photosensitive member; 
 a light source configured to emit a light beam based on image data to form an electrostatic latent image on the photosensitive member; 
 a deflecting unit configured to deflect the light beam so that the light beam scans the photosensitive member, the deflecting unit comprising a rotary polygon mirror and a motor configured to rotate the rotary polygon mirror; 
 an estimating unit configured to estimate a rise time of the motor; and 
 a control unit configured to pre-rotate the rotary polygon mirror before a start signal for instructing a start of image formation is generated, and configured to rotate, after the start signal is generated, the rotary polygon mirror at a rotation speed which is higher than a rotation speed for pre-rotation of the rotary polygon mirror, 
 wherein the control unit sets a target value of the rotation speed for the pre-rotation of the rotary polygon mirror based on a result of estimation by the estimating unit. 
 
     
     
       12. An image forming apparatus according to  claim 11 ,
 wherein the estimating unit comprises a temperature detecting unit configured to detect an ambient temperature of the motor, and 
 wherein the control unit sets the target value based on a result of detection by the temperature detecting unit. 
 
     
     
       13. An image forming apparatus according to  claim 11 ,
 wherein the estimating unit comprises a lapsed time obtaining unit configured to obtain a lapsed time from when a previous image formation is completed until a current rotation of the motor is started, and 
 wherein, when the lapsed time obtained by the lapsed time obtaining unit is a first time period, the control unit sets the target value to a first rotation speed, and, when the lapsed time obtained by the lapsed time obtaining unit is a second time period which is shorter than the first time period, the control unit sets the target value to a second rotation speed which is lower than the first rotation speed. 
 
     
     
       14. An image forming apparatus according to  claim 11 ,
 wherein the estimating unit comprises a total operation time obtaining unit configured to obtain a total operation time of the motor, and 
 wherein, when the total operation time obtained by the total operation time obtaining unit is a first time period, the control unit sets the target value to a first rotation speed, and, when the total operation time obtained by the total operation time obtaining unit is a second time period which is shorter than the first time period, the control unit sets the target value to a second rotation speed which is lower than the first rotation speed.